In recent years, expectations are placed on development of a robot arm capable of a higher-level and complex task on various objects like a human being. An active research is conducted on detection of the magnitude or the direction of a load applied to a contact surface by the use of a load sensor or a tactile sensor so that a robot can steadily grasp a complicated shaped object (such as a soft thing or a complicated shaped body) without braking or falling the object by slipping.
Conventionally, there is known a sensor that is attached to the side surface of a convexly shaped elastic body in order to three-dimensionally detect the magnitude and the direction of application of a load. When loaded, the sensor can detect the magnitude and the direction of a load by detecting distortion applied to a convex portion of the elastic body.
For example, patent literature 1 forms a sensor on the side surface of a convex portion of an elastic body by fabricating the sensor on a thin film and using an adhesive material to attach the sensor to the convex portion of the elastic body whose side surface is trapezoidally shaped.
Specifically, a human tactile sense is known to exist at the density of one tactile sense per mm2. For this reason, load sensors need to be integrated at the density of one sensor per mm2 in order to achieve the advanced tactile sense capability like a human being.
However, the configuration described in patent literature 1 requires a process that uses an adhesive material to attach a thin film where the sensor is formed, leaving an issue of difficulty in miniaturization and high-density formation.
There is a technology that forms a thin-film organic vertical transistor on the side of a rib. A combination of this technology with the configuration described in patent literature 1 can use the thin-film technology to form a vertical transistor on the side surface of a rib that is shaped in to a trapezoid (slope of 60°). However, this configuration still leaves difficulty in separation between detection of a vertical load applied to the rib from above and detection of a horizontal load applied over a rib surface.